pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-sccp/+/31825 )
Change subject: Avoid allocating conn_id 0x00FFFFFF ......................................................................
Avoid allocating conn_id 0x00FFFFFF
The 0x00FFFFFF source local reference is reserved in M3UA/SCCP, hence avoid allocating a conn_id with that value since later on when reused as a source local reference it would fail to be encoded.
Change-Id: Ifcf710ef6024286a1cc3473d6ea3f858552b9926 --- M src/sccp_scoc.c 1 file changed, 28 insertions(+), 3 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-sccp refs/changes/25/31825/1
diff --git a/src/sccp_scoc.c b/src/sccp_scoc.c index 00e677c..2430462 100644 --- a/src/sccp_scoc.c +++ b/src/sccp_scoc.c @@ -507,10 +507,22 @@ { uint32_t conn_id;
+ /* SUA: RFC3868 sec 3.10.4: + * The source reference number is a 4 octet long integer. + * This is allocated by the source SUA instance. + * M3UA/SCCP: ITU-T Q.713 sec 3.3: + * The "source local reference" parameter field is a three-octet field containing a + * reference number which is generated and used by the local node to identify the + * connection section after the connection section is set up. + * The coding "all ones" is reserved for future use. + * Hence, as we currently use the connection ID also as local reference, + * let's simply use 24 bit ids to fit all link types (excluding 0x00ffffff). + */ do { - /* modulo 2^24 as we currently use the connection ID also as local - * reference, and that is limited to 24 bits */ - user->inst->next_id = (user->inst->next_id + 1) % (1 << 24); + /* Optimized modulo operation (% 0x00FFFFFE) using bitwise AND plus CMP: */ + user->inst->next_id = (user->inst->next_id + 1) & 0x00FFFFFF; + if (OSMO_UNLIKELY(user->inst->next_id == 0x00FFFFFF)) + user->inst->next_id = 0; conn_id = user->inst->next_id; } while (conn_find_by_id(user->inst, conn_id));
-
pespin